1. Field of the Invention
The invention relates generally to the formation of metal items and specifically to reinforcing drawn or stretched metal items.
2. Description of the Related Art
Metal items are frequently fabricated from sheets of metal stock that are punched, trimmed, stamped, and/or drawn into the finished item. The fabrication process frequently involves progressively forming the item in a sequence of manufacturing steps, which may include punching openings into the stock, trimming material from the stock, and stamping or drawing the item into the finished configuration through the use of molds, dies, presses, and the like. The process of stretching the metal can introduce areas of weakness in the finished item, particularly in portions where an annulus is drawn. In such situations, stamping or drawing operations can stretch the stock into areas of relative thinness, which consequently have an increased susceptibility to fatigue and corrosion, thereby shortening the useful life of the item.
Selected portions of items fabricated in this way are frequently reinforced by adding supplemental material in selected areas, typically by welding or brazing operations. Alternatively, parts of the item that are susceptible to such weakness can be separately fabricated in order to avoid the stretching and thinning of the material, and then attached to the item. However, both of these techniques add fabrication steps, increase the handling of the item, and increase the complexity and cost of fabricating the item. Another recognized method of maintaining strength in a stretched metal item is to increase the base metal stock thickness so that all drawn portions exceed specifications. But the consequent item will cost more and weigh more, resulting in needless waste. There is a need for reinforcing portions of an item that have been weakened as a result of a stretching operation in a manner that is easy to fabricate and relatively inexpensive.